The objectives of the proposed project are 1) to outline the biochemical and antigenic parameters of Equine Infectious Anemia virus which define its relationship to the other members of the 'slow virus' group and the oncogenic RNA viruses, and 2) to more completely evaluate the function of the immune system, both humoral and cellular in infected animals, and 3) attempt to relate the findings of these studies to mechanisms of viral persistence in EIA. The methods will include biochemical studies of the RNA genome of the virus, attempt to demonstrate an RNA-dependent DNA polymerase in the virion, and an analysis of the polypeptide profile of the viral proteins by polyacrylamide gel electrophoresis. A comparative antigenic analysis will be conducted between EIA virus and RNA tumor viruses, as well as the 'slow' RNA viruses, in an attempt to uncover any antigenic relatedness. The surface and oncogenic potential of the persistently infected diploid cell line will be evaluated by lectin agglutinability, immunologic techniques and injection into hamster cheek pouches. Immunologic evaluation of the cellular immune mechanism will be performed using H3-thymidine uptake by sensitive cells in the presence of cell-culture produced viral antigen. Preparations of viral-antigen- containing membranes from infected cells will be used to attempt to induce resistence to infection.